Quick action couplings of the cam-locking type have been in use for many years for the purpose of interconnecting pipes, hoses and other conduits used for the purpose of conveying liquids and dry bulk products under low to medium pressures. The conventional coupling of this type, as described in military standard MIL-C-27487 comprises a female coupling member on which a pair of cam arms are pivotally mounted in openings extending through the coupling wall. The cam arms have camming surfaces which project through the openings and are adapted to interengage with a groove of arcuate cross-section in an interfitting male coupling member. In an initial position in which the male coupling member is inserted into the female coupling member, the cam arms are held so that they project radially outwardly from the coupling allowing clearance for the male coupling member to be inserted, which is accomplished by moving the female coupling member towards and over the male coupling member. As the female coupling member is pushed towards the male coupling member, the cam arms are drawn in the opposite direction towards the worker until they ultimately extend parallel to the axis of the coupling. This draws the male coupling member further into the female coupling member compressing a compressible sealing ring against an annular shoulder within the female coupling member, thereby effecting a seal.
Several difficulties are encountered in the use of this type of coupling assembly. Interconnecting the coupling parts requires that the worker exert a force on the female coupling member towards the male coupling member and while maintaining this force, apply a force to the cam arms in the opposite direction to effect a locking of the coupling parts in place. In practice, particularly with the larger sizes of couplings, this is not always easy to do, especially in very cold weather when a workman is wearing heavy gloves. Considerable jockeying of the female member is often required to align the cam surfaces within the groove. If not properly aligned and the workman attempts to force the cam arms to the locking position, there is a likelihood that one or both cam arms will become bent or even broken. In addition to the foregoing, the cam arms are often subject to breaking or bending when the parts are uncoupled and the cam arms not securely fastened. Once bent, replacement of the cam arms is the only option available.
Other types of couplings of the quick action type are known, which involve the use of spheres carried in openings extending through the wall of the female coupling member. A locking sleeve or collar is spring loaded into a position in which the balls are held so that they interfit in a recess in the outer periphery of the male coupling member. In known couplings of this type, sealing is accomplished by a spring-loaded gasket or sealing ring. The spheres do not act to draw the male coupling member into engagement with the seal. They do not contribute to the sealing force and only serve as locking members.